The cross-party committee has been examining plans to replace GCSEs with English Baccalaureate certificates.

The government said it was "making major changes to ensure we have world class exams that raise standards".

'Damaged brand'

The committee's report raises doubts about the pace and direction of the shake-up planned for GCSEs.

It said there were so many worries, it should act as a "red light" to the government.

The government says it wants to abolish GCSEs for core subjects and introduce English Baccalaureate certificates from 2015. There will also be only one exam board for each subject.

No sensible reform of assessment can take place without clarity as to what is to be taughtGraham Stuart, Education Select Committee chairman

But the committee said the government had failed to prove such a change was necessary.

It also raised concerns about introducing English Baccalaureate certificates in English, maths and science while still running "discredited" GCSEs for other subjects.

The committee's report said it agreed with many of the plans to overhaul GCSEs - such as moving exams to the end of a course and limiting the culture of excessive resits.

But it rejected the idea that GCSEs were such a "damaged brand" that they needed to be abolished.

The committee also questioned the "coherence" of introducing changes to GCSEs before deciding the accompanying national curriculum.

It called on the government to publish its plans for the secondary curriculum "as soon as possible".

"No sensible reform of assessment can take place without clarity as to what is to be taught. Coherence is not achieved by accident but by design," said Graham Stuart, the committee chairman and Conservative MP.

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Media captionCommittee chair and Tory MP Graham Stuart: "We're not sure the government has thought this through properly"

There are also strong concerns about the speed of so many proposed changes - and the pressures that it will place on the exam system.

The report pointed to the controversy of last summer's English GCSE results as an example of the "turbulence" that could be caused by changes to the exam system.

The timetable was "not merely challenging but so tight that it may risk endangering the quality", it said.

'Untenable'

The report said the government should consider Ofqual's recommendation that moving to a single exam board for each subject should be "decoupled" from the overhaul of qualifications.

The MPs urged caution when considering upheavals in exams.

We have been clear that the secondary education system is in desperate need of a thorough overhaulDepartment for Education

"We recommend that the government takes time for careful consideration and slows down the pace of change," the committee's report concluded.

The report also highlighted the opposition of "stakeholders" in education to the reforms - and the responses from teachers' union reflected this hostility.

The National Union of Teachers' leader, Christine Blower, said the government's position on exam reform was "now surely untenable".

"The education secretary is totally isolated in his view that the English Baccalaureate certificates are a suitable measure to replace GCSEs," she said.

Chris Keates, of the NASUWT teachers union, accused the government of displaying "arrogant disregard for the impact on the lives of young people".

Labour leader Ed Miliband said there was "a groundswell against Michael Gove's plan" because he was "squeezing creativity out of the curriculum".

"Also he's not really focusing on those kids who maybe aren't going to go to university but need high quality vocational qualifications," said Mr Miliband.

'Thorough overhaul'

Dr Mary Bousted, head of the Association of Teachers and Lecturers, said: "This is a devastating critique of the government's policy. Michael Gove will lack any credibility if his response is 'I know best; carry on.'

"The parliamentary committee now joins a long list of those who publicly oppose the plans."

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Media captionRussell Hobby, from the National Association of Head Teachers, suggests the plans do not address the problems with exams

But the Department for Education said the report accepted the need for major improvements.

"We have been clear that the secondary education system is in desperate need of a thorough overhaul - an objective with which the committee agrees," said an education department spokeswoman.

"That why we are making major changes to ensure we have world class exams that raise standards."